| Regulation of histone methylation levels has long been implicated in multiple cellular processes, including transcription, silencing, sex chromosome regulation and DNA damage repair. The histone lysine demethylase LSD1 has been studied in a variety of model systems, although most of these studies have focused on its transcriptional activities. The genome of the nematode C. elegans contains two putative LSD1 orthologs, spr-5 and T08D10.2, as well as one ortholog of LSD2, amx-1. Based on previous reports of a potentially meiotic phenotype in various model systems, we set out to determine if any of these orthologs had a role in C. elegans meiosis. In this work, we report a novel role for the C. elegans histone demethylase SPR-5 in meiotic DNA double-strand break repair (DSBR), as well as a germline-specific role in transcriptional regulation. SPR-5 shows enzymatic activity towards H3K4me2 both in vitro and in the nematode germline, and spr-5 mutants show several phenotypes indicating a perturbation of DSBR, including increased p53-dependent germ cell apoptosis, increased levels of the DSBR marker RAD-51, and sensitivity towards DSB-inducing treatments. SPR-5 also shows a rapid sub-cellular re-localization upon DSB-inducing treatment, which suggests SPR-5 may function directly in DSBR. Finally, by using a germlinc-specific microarray analysis followed by qRT-PCR of candidate genes, we identified 130 misregulated genes in spr-5 mutant germlines, with 126 upregulated. Comparison of this gene list to published arrays identified several sets of somatic-expressed genes that were upregulated in spr-5 mutant germlines, but no genes with any reported role in DSBR. Our data therefore supports a role for spr-5 in repressing somatic genes in the germline, including some with germline function. Taken together, our results demonstrate at least two functions for spr-5: one in promoting meiotic double-strand break repair, and one in repressing somatic genes in the germline, supporting the model that chromatin-modifying enzymes can have multiple functions in vivo, in the same tissue. |
